Policy makers do not know how to alter the structure and process of primary care to provide treatment which will improve and sustain improvement in the functional impairment associated with major depression, the fourth leading cause of disability worldwide. To address this problem, we propose the Quality Improvement for Depression (QID). The specific aims of QID are: (1) to provide integrated analyses of the long term impact of four distinct but related primary care interventions to improve depression treatment during the acute, continuation, and maintenance phase of care; and (2) to estimate the effects of high quality primary care depression treatment on long term disability. In the early stages of QID collaboration, funded investigators of four separately conceived quality improvement interventions planned and implemented a coordinated strategy for recruitment, intervention, and data collection in 108 primary care clinics in network and staff model HMOs, IPAs, PPOs, and mixed model settings. In addition to common baseline organizational and provider data, QID investigators are collecting over 80 common variables from 1,980 patients with major depression at each of three waves across the first year. This application seeks support to conduct effectiveness analyses in the combined database after standardizing patient follow-up during the second year across the four projects. This effort is needed to understand the "big picture" of how four dissemination interventions which are feasible to integrate across a variety of practice settings and populations, impact the quality and outcome of care, with sufficient power to determine whether they improve outcomes over a duration meaningful to policy makers. The analyses will inform policy debates about effective mental health treatment by providing generalizable estimates of the effect of antidepressant medication and psychotherapy on disability over the long term.